RF photonics enables improved sensitivity and signal processing capabilities for the collection and transmission of RF data. The enabling component in RF photonics is the electro-optic modulator, which imprints the RF signal onto an optical carrier. Transmission and processing of RF signals in the photonic domain provides the advantages of photonics, such as large bandwidth, low transmission loss over long distances, and lower size, weight, and power (SWaP) consumption of the device or subsystem.
A multitude of RF waveform synthesis and complex RF filtering functions have been demonstrated using photonics. More recently, complex photonic devices for RF beamforming or programmable filters have been studied on both centimeter sized silicon and silicon nitride photonic chips.
The efficiency of transferring RF signals onto an optical carrier depends on the voltage sensitivity of the modulator, expressed as Vπ, which is the voltage required to drive a half-wave phase shift in the optical signal. The voltage Vπ impacts the energy efficiency of a photonic link, the achievable device size, as well as signal quality metrics such as the noise figure. Conventionally, voltage efficiencies of about 1-2 V with a bandwidth of 10 GHz limit the magnitude and spectrum of RF signals that can be processed without pre-amplification and channelization in the RF domain. This results in a critical bottleneck for realizing the full potential of RF photonics.
Accordingly, there is a need in the art for addressing the limitations of conventional electro-optic modulators with respect to the efficiency, voltage sensitivity, and performance of RF photonics systems, and for addressing the foregoing as well as other drawbacks of conventional systems.